The overall aim of this project is to identify mechanisms by which the transcription of ribosomal RNA and protein genes is co- ordinated in eukaryotes, using Neurospora crassa as a model system. Previously this lab has shown that Neurospora crassa 5S and 40SrRNA genes require a common sequence, the ribo box, for transcription in vitro, and that a Neurospora ribosomal protein gene crp-2 contains three ribo boxes in its 5' flanking sequences. This proposal is designed to test the hypothesis that the protein that binds to the ribo box co-ordinates the transcription of 5S rRNA, 40S rRNA and ribosomal protein genes in Neurospora. It is proposed to test the regulatory role of the ribo box by placing rRNA and r-protein genes with ribo box mutations back into Neurospora and measuring their transcription and regulation in vivo, and by introducing ribo boxes into unrelated genes such as qa-2 and tRNAleu, and testing the effects of those additions on the regulation of those genes in vivo. To examine the molecular action of the ribo box it is proposed to purify the ribo box-binding protein and to characterize its properties, and to attempt the cloning of the gene coding for this protein.